The present invention relates to a face-seal fitting employing a metal gasket for connecting conduits used in applications requiring special cleanliness, wherein the fitting has minimum dead volume at the interior of the conduits.
Face-seal fittings in the prior art employed gaskets which were in the form of simple circular annuluses, the shape of which provided no aid in alignment or in sealing, or which had a substantial surface or area projecting inside the seal, thereby defining crevices, or dead volumes, which were subject to the problem of entrapping material from the fluid carried by the fitting in which the gasket was employed. Such entrapped material can accumulate and later break off and flow with a fluid conveyed by the fitting, thereby contaminating semiconductor or other materials requiring special cleanliness.
A gasket disclosed in U.S. Pat. No. 4,854,597 issued to Leigh improves over the gaskets of the prior art in that a region of the gasket with conical, or bevel, faces connects a wider outer ring and a narrower inner ring which both have sidewalls perpendicular to an axis formed by the tubular members. This shape causes the elements of the fitting to align with the gasket so that a uniform sealing force on both sides of the gasket is achieved. Moreover, by virtue of the fact that the bead is rounded in axial cross section, sealing is provided along a single high-pressure line of contact, which enables a large sealing force to be applied on each side of the gasket. These advantages are provided while at the same time only a small area of the gasket projects into the fluid stream so that there is little area for entrapping material from said fluid flowing through the fitting.